The recent printk rework introduced a new type of console NBCON that will perform printing via a dedicated kthread during normal operation. For times when the kthread is not available (early boot, panic, reboot/shutdown) the NBCON console will print directly from the printk() calling context (even if from NMI). Futher details about NBCON consoles are available here [0]. This series converts the 8250 driver to an NBCON console, providing both threaded and atomic printing implementations. Users can verify the UART console is an NBCON console via the proc filesystem. For example: $ cat /proc/consoles ttyS0 -W- (EC N a) 4:64 The 'N' shows that it is an NBCON console. There will also be a dedicated printing kthread. For example: $ ps ax | grep pr/ 16 root 0:00 [pr/ttyS0] Derek Barbosa performed extensive tests [1] using this driver and encountered no issues. On the contrary, his tests showed the improved reliability and non-interference features of the NBCON-based driver. Since this is the first console driver to be converted to an NBCON console, it may include variables and functions that could be abstracted to all UART consoles (such as the @console_newline_needed field). However, we can abstract such things later as more consoles are converted to NBCON. John Ogness [0] https://lore.kernel.org/lkml/20230302195618.156940-1-john.ogness@xxxxxxxxxxxxx [1] https://lore.kernel.org/lkml/ZsdoD6PomBRsB-ow@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx John Ogness (2): serial: 8250: Switch to nbcon console serial: 8250: Revert "drop lockdep annotation from serial8250_clear_IER()" drivers/tty/serial/8250/8250_core.c | 42 +++++++- drivers/tty/serial/8250/8250_port.c | 151 +++++++++++++++++++++++++++- include/linux/serial_8250.h | 6 ++ 3 files changed, 196 insertions(+), 3 deletions(-) base-commit: f1ec92a066b2608e7c971dfce28ebe2d2cdb056e -- 2.39.2
